Mac Id Authentication for HR Employee Information

Transcription

1 Mac Id Authentication for HR Employee Information [ Master Project 2007] Under the guidance of Prof. Gonhsin Liu Submitted by: MANOJ DUVVA (ID# )

2 Abstract Today the web technology is growing rapidly and so with it the threat of intruder hacking the system. Companies to day depend hugely on web technology for sharing important information inside the companies. One such information system is employee information.for example Information like his personnel contacts, his qualification, his performance details etc. so net becomes a very unsafe place to host such information on system. So it s our responsibility to think one step ahead. All computers has a Unique Mac-address.So if we can trace what is Mac address of the client system then we can make sure it system trying to access the site is valid or not. For example suppose if an unauthorized person gets valid login and password of such site even then he can t access the system unless he login from authorized machine. This is nothing but to make sure that both the machine and the login user both are authorized. So I am planning to develop a web application which has all contains all Human Recourse related information of all the employees in an organization and implement Mac-address base authentication in this site. HARDWARE REQUIREMENTS: - Pentium Min. 233 MHz. 32 MB Ram 512 KB Cache Memory Hard disk 4.3 GB Microsoft Compatible 101 or more Key Board SOFTWARE REQUIREMENTS: - Operating System : Windows 98/NT/XP Back End : MS SQL SERVER &MS EXCELSHEET Front End : Microsoft Visual studio 2005 (ASP.NET) Database Connectivity : Microsoft ODBC Driver.

3 Overview: This project deals with the collection of HR employee information (database).but this is a secured site so that if any one even knows the login id and the password but he cannot open this any other machine. Here our system s Mac Id is authenticated with this site. The same login id and the password in the same machine can only be operated. Here we can create a role such a ways that his user id and password and his Mac id is required to create a role. In this way the user is created. Even this site has different roles for a user. A user can be given different permission such that he can only read the data but not edit the data. Even a user can be given permission on the access of only specific pages. Here the data is imported for an Excel page. First the date is entered in an formatted Excel sheet. Then through this project it can be edited and deleted depending the user logged on and by submitting the changes it effects in the database. Learnt from this Project: Visual studio.net 2005 Sql server 2000 Database Analyzing a Problem

4 Introduction: What is a MAC Address A MAC address is a unique number assigned to a Network Interface Card (NIC), commonly called an Ethernet card. This "address" is created by the manufacturer. A MAC address is a 12-digit number. Each digit is a number from 0-9 or a letter from A-F. Sometimes the digits of a MAC address are separated by colons or dashes. Examples of possible MAC addresses include: A92BFC, 09:00:07:A9:B2:EB, or A-B9-E2-A4. In Windows, how do I check my computer's IP address or physical (MAC) address? Windows NT, 2000, and XP To see what IP address, default gateway, and subnet mask your computer is using: 1. Click the Start button and select All Programs (XP) or Programs (NT and 2000). 2. Select Accessories, then Command Prompt (2000 and XP), or Command Prompt (NT). 3. At the command prompt, enter: ipconfig 4. To close the command prompt, enter: exit

5 For other IP information on Windows, including the physical address, at the command prompt, enter: ipconfig /all more This will give you information regarding your computer's TCP/IP setup, including: Host name DNS servers Physical address IP address Subnet mask Default gateway WINS servers The IP address will be a series of numbers following the pattern xxx.xxx.xxx.xxx, for example, The physical address, which many people call the MAC address, will be a series of six hexadecimal number pairs following the pattern xx-xx-xx-xx-xx-xx, for example, A4-F3-C0-01. Windows XP, without using the command prompt Alternatively, in Windows XP, if you want to find this information and want to stay within the graphic user interface, or for any reason do not want to use DOS commands, you can find this information by doing the following: 1. Right-click the My Network Places icon, and then select Properties. 2. Double-click the Local Area Connection icon. Occasionally, there will be a number on the end (e.g., Local Area Connection 2); it depends on your computer's configuration. If you are looking for the MAC address for

6 a wireless adapter, the icon will normally be named Wireless Network Connection. 3. Click the Support tab. 4. Click the Details... button. The physical address (MAC address) and IP address will be listed in the window that appears. Windows 95, 98, and Me To check your computer's IP address or physical address, follow the steps below: 1. Click the Start button and select Run Type winipcfg and click OK. 3. From the drop-down menu, select the adapter being used for your connection: o o o Select PPP Adapter if you're dialing in. Select the Ethernet adapter if you're connected to a LAN or a broadband connection. Select the wireless adapter if you're connected via wireless. The IP address will appear in its labeled field. The MAC address will appear in a field labeled Adapter Address. Alternatively, you may follow these steps: 1. Click the Start button and select Settings, then Control Panel. 2. Double-click Network. Select TCP/IP, then click Properties. The IP address appears under the IP Address page tab.

7 About Database Access: A database is a collection of information related to a particular subject or purpose, such as tracking customer orders or maintaining a music collection. If your database isn't stored on a computer, or only parts of it are, you may be tracking information from a variety of sources that you're having to coordinate and organize yourself. Using Microsoft Access, you can manage all your information from a single database file. Within the file, divide your data into separate storage containers called tables; view, add, and update table data using online forms; find and retrieve just the data you want using queries; and analyze or print data in a specific layout using reports. To store your data, create one table for each type of information you track. To bring the data from multiple tables together in a query, form, or report, you define relationships between the tables. To find and retrieve just the data that meets conditions you specify, including data from multiple tables, create a query. A query can also update or delete multiple records at the same time, and perform built-in or custom calculations on your data. Import Data OR Link Data : Microsoft Access can import or link table data from other Microsoft Access databases, as well as data from other programs and file formats, such as Microsoft Excel, dbase, Microsoft FoxPro, or Paradox. You can also import or link

8 (read-only) HTML tables and lists, which can reside on your local computer, a network server, or an Internet server. Importing data creates a copy of its information in a new table in your Microsoft Access database. The source table or file is not altered in this process. Linking data enables you to read and in most cases update data in the external data source without importing. The external data source's format is not altered so that you can continue to use the file with the program that originally created it, but you can add, delete, or edit its data using Microsoft Access as well. When importing data, you can't append data to existing tables (except when importing spreadsheet or text files). However, once you have imported a table, you can perform an append query to add its data to another table. Exporting Data: Export data from a table or query to many different formats. You can also export any of your database objects to another Microsoft Access database. This is effectively the same as copying and pasting objects between databases. You can export tables, queries, forms, and reports to HTML files, or tables, queries, and forms to IDC/HTX files, which you can then use as part of a World Wide Web site. TABLES: A table is a colletion of data about a specific topic, such as products or suppliers. Using a separate table for each topic means we can store that data only once, which makes your database more efficent and reduces data-entry errors. Tables organize data into coloumns and rows.

9 In table Datasheet view, you can add, edit, or view the data in a table. You can also check the spelling and print your table's data, filter or sort records, change the datasheet's appearance, or change the table's structure by adding or deleting columns. In table Design view, you can create an entire table from scratch, or add, delete, or customize an existing table's fields. QUERIES: Use queries to view, change, and analyze data in different ways. You can also use them as the source of records for forms and reports. The most common type of query is a select query. A select query retrieves data from one or more tables using criteria you specify, and then displays it in the order you want. We create a query with a wizard or form scrach in query Design view. In Design view, we have to specify the data you want to work with by adding the tables or queries that contain the data, and then by filling in the design grid. REPORTS: A report is an effective way to present your data in a printed format. Because you have control over the size and appearance of everything on a report, you can display the information the way you want to see it. Most of the information in a report comes from an underlying table, query, or SQL statement, which is the source of the report's data. Other information in the report is stored in the report's design. We can create the link between a report and its record source by suing graphical objects called controls. Controls can be text boxes that display names

10 and numbers labels that display titles, and decoperative lines that graphically organize the data and make he report more attractive. Macros: A macro is a set of one or more actions that each perform a particular operation, such as opening a form or printing a report. Macros can help you to automate common tasks. For example, you can run a macro that prints a report when a user clicks a command button. A macro can be one macro composed of a sequence of actions, or it can be a macro group. You can also use a conditional expression to determine whether in some cases an action will be carried out when a macro runs.

11 INTRODUCTION TO SQL Structured Query Language (SQL), is the set of commands That all programs and users must use to access data within the Oracle database. Application programs and Oracle tools often allow users to access the database without directly using SQL, but these applications in turn must use SQL when executing the user's request. This chapter provides background information on SQL used by most relational database systems. Topics include: History of SQL SQL Standards How SQL Works History of SQL The paper, "A Relational Model of Data for Large Shared Data Banks," by Dr. E. F. Codd, was published in June 1970 in the Association of Computer Machinery (ACM) journal, Communications of the ACM. Codd's model is now accepted as the definitive model for relational database management systems (RDBMS). The language, Structured English Query Language (SEQUEL) was developed by IBM Corporation, Inc. to use Codd's model. SEQUEL later became SQL. In 1979, Relational Software, Inc. (now Oracle Corporation) introduced the first commercially available implementation of SQL. Today, SQL is accepted as the standard RDBMS language. SQL Standards Oracle SQL complies with industry accepted standards. Oracle Corporation ensures future compliance with evolving SQL standards by actively involving key personnel in SQL standards committees. Industry accepted committees are the American National Standards Institute (ANSI) and the International Standards Organization (ISO), which is affiliated with the International Electrotechnical

12 Commission (IEC). Both ANSI and the ISO/IEC have accepted SQL as the standard language for relational databases. When a new SQL standard is simultaneously published by these organizations, the names of the standards conform to conventions used by the organization, but the technical details are exactly the same. How SQL Works This section describes many of the reasons for SQL's widespread acceptance by relational database vendors as well as end users. The strengths of SQL benefit all ranges of users including application programmers, database administrators, management, and end users. Technically speaking, SQL is a data sub language. That is to say, the purpose of SQL is to interface to a relational database such as Oracle, and all SQL statements are instructions to the database. In this it differs from general purpose programming languages like C and Basic. Among the features of SQL are the following: It processes sets of data as groups rather than as individual units. It provides automatic navigation to the data. It uses statements that are complex and powerful individually, and that therefore stand alone. Flow-control statements were not part of SQL originally, but they are found in the recently accepted optional part of SQL, ISO/IEC : Flow-control statements are commonly known as "Persistent Stored Modules" or PSM, and Oracle's PL/SQL extension to SQL is close to PSM. Essentially, SQL lets you work with data at the logical level, only being concerned with the implementation details when you want to manipulate them. SQL provides commands for a variety of tasks including:

13 querying data inserting, updating, and deleting rows in a table creating, replacing, altering, and dropping objects controlling access to the database and its objects guaranteeing database consistency and integrity SQL unifies all of the above tasks in one consistent language. Oracle and Standard SQL This appendix discusses the following topics: Oracle's conformance to the SQL standards established by industry standards governing bodies Oracle's extensions to standard SQL Locating extensions to standard SQL with the FIPS Flogger Introduction to Data Definition Language The data Definition Definition Language is used to create an object, alter the structure of an object and also to drop the table created. A table is a unit of storage which holds data in the form of rows and columns. The DDL can be classified in to following categories. Create table command Alter table command Drop table command 1. Create: This command is used to create a table in the data base. Create table <table name>(column definition1,column definition2,...);

14 2. Alter command: Alter command cater to the need of the following situations. A) When the user wants to add a new column to the existing table. Alter table <table name> add (column definition...); B) When the user wants to modify the existing column definition. Alter table <table name> modify (column definition...); 3. Drop table command: This command is used to drop the table from the data base. Drop table <table name>; DATA MANIPULATION LANGUAGE COMMANDS: Data Manipulation Commands are most frequently used SQL commands. They are as follows, Insert Select Update Delete Insert Command: This command is used to to add one or more rows to the table. While using this command the values are seperated by commas and the datatypes char and date are enclosed in apostrphes. The values must be entered in the same order as they are defined in the table. Insert into <table name> values (a list of data values);

15 SELECT COMMAND: To perform a query we use the select command. The query is a request for the information. It is the most common data base operation used. Select column name... from <table name>; Or Select * from <table name>; It will give all the information in the table. UPDATE COMMAND: Update command is used to alter the column values in the table. The update command consists of a set clause and an optional where clause. Update <table name> set field=value,... where condition; e.g. update emp set sal=10000 where name= Reddy ; Delete Command: This command is used to delete several rows from the table. After inserting rows in a table we can also delete then if required. The delete command consists of a from clause followed by an optional where clause. Delete from <table name> where conditions;

16 Transaction control commands: Commit: This command is used to end a transaction. Commit work; Or Commit; Rollback: A rollback command is used to undo the work done in the current transaction. Rollback; GRANT The GRANT command (System Privileges and Roles) is an extension to standard SQL. The GRANT command (Object Privileges) supports the following other privileges on other objects in addition to the DELETE, INSERT, REFERENCES, SELECT, and UPDATE privileges on tables and views supported by Entry SQL-92: ALTER EXECUTE INDEX READ This command also supports granting object privileges to roles. Operators This section describes additional operators and additional functionality of standard operators. Additional Operators Oracle supports these operators that are not part of Entry SQL-92:

17 character operator (character concatenation)!=, ^=, and = comparison operators (inequality) MINUS set operator INTERSECT set operator (+) operator (outer join) INTEGRITY CONSTRAINTS An integrity constraint is a mechanism used by Oracle to prevent invalid data entry into the table. The following are the various types of integrity constraints. Domain integrity constraint a) Not Null constraint b) Check constraint Unique constraint Referential integrity constraint 1. Not Null : When a Not Null constraint is enforced on a column or a set of columns in a table, it will not allow Null values. e.g. create table <table name>(column definition1 constraint <constraint name>not Null, column definiton2,...); 2. Check constraint: These are rules governed by logical or boolean expression. e.g. create table emp(eid number(4) constraint con check(eid>100));

18 3. Unique constraint: This constraint is used to prevent the duplication of values within the rows of a specified column in the table. e.g. create table emp(eid number(4) constraint con unique); Primary Key Constraint: This constraint avoids duplication of rows and does not allow Null values, when enforced in a column or set of columns. create table emp(eid number(4) constraint con primary key); 4. Referential Integrity Constraint: To establish a parent-child or a master-detail relationship between two tables having a common column, we make use of referential integrity constraints. Basic components related to this constraint are: Foreign Key: A column or combination of columns include in the definition of referential integrity which would refer to a referenced key. Referenced Key: It is a unique or primary key which is defined oa a column belonging to the parent table. Child Table: This table depends upon the values present in the referenced key of the parent table, which is referred by a foreign key. Parent table:

19 This table determines insertion or updation of data can be done in child table. This table would be referred by child s table foreign key. e.g. create table emp(eid number(4) constraint con references dept(deptid)); On Delete Cascade clause If all the rows under the referenced key column in a parent table are deleted, then all rows in the child table with dependent foreign key column will also be deleted automatically. e.g. create table emp(eid number(4) constraint con references dept(deptid) on delete cascade);

20 Overview of the.net Framework The.NET Framework is a new computing platform that simplifies application development in the highly distributed environment of the Internet. The.NET Framework is designed to fulfill the following objectives: To provide a consistent object-oriented programming environment whether object code is stored and executed locally, executed locally but Internet-distributed, or executed remotely. To provide a code-execution environment that minimizes software deployment and versioning conflicts. To provide a code-execution environment that guarantees safe execution of code, including code created by an unknown or semi-trusted third party. To provide a code-execution environment that eliminates the performance problems of scripted or interpreted environments. To make the developer experience consistent across widely varying types of applications, such as Windows-based applications and Web-based applications. To build all communication on industry standards to ensure that code based on the.net Framework can integrate with any other code. The.NET Framework has two main components: the common language runtime and the.net Framework class library. The common language runtime is the foundation of the.net Framework. You can think of the runtime as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness. In fact, the concept of code management is a fundamental principle of the runtime. Code that targets the runtime is known as managed code, while code that does not target the runtime is known as unmanaged code. The class library, the other main component of the.net Framework, is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI)

21 applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services. The.NET Framework can be hosted by unmanaged components that load the common language runtime into their processes and initiate the execution of managed code, thereby creating a software environment that can exploit both managed and unmanaged features. The.NET Framework not only provides several runtime hosts, but also supports the development of third-party runtime hosts. For example, ASP.NET hosts the runtime to provide a scalable, server-side environment for managed code. ASP.NET works directly with the runtime to enable Web Forms applications and XML Web services, both of which are discussed later in this topic. Internet Explorer is an example of an unmanaged application that hosts the runtime (in the form of a MIME type extension). Using Internet Explorer to host the runtime enables you to embed managed components or Windows Forms controls in HTML documents. Hosting the runtime in this way makes managed mobile code (similar to Microsoft ActiveX controls) possible, but with significant improvements that only managed code can offer, such as semi-trusted execution and secure isolated file storage. The following illustration shows the relationship of the common language runtime and the class library to your applications and to the overall system. The illustration also shows how managed code operates within a larger architecture.

22 The following sections describe the main components and features of the.net Framework in greater detail. Features of the Common Language Runtime The common language runtime manages memory, thread execution, code execution, code safety verification, compilation, and other system services. These features are intrinsic to the managed code that runs on the common language runtime. With regards to security, managed components are awarded varying degrees of trust, depending on a number of factors that include their origin (such as the Internet, enterprise network, or local computer). This means that a managed component might or might not be able to perform file-access operations, registry-access operations, or other sensitive

23 functions, even if it is being used in the same active application. The runtime enforces code access security. For example, users can trust that an executable embedded in a Web page can play an animation on screen or sing a song, but cannot access their personal data, file system, or network. The security features of the runtime thus enable legitimate Internet-deployed software to be exceptionally feature rich. The runtime also enforces code robustness by implementing a strict type- and codeverification infrastructure called the common type system (CTS). The CTS ensures that all managed code is self-describing. The various Microsoft and third-party language compilers generate managed code that conforms to the CTS. This means that managed code can consume other managed types and instances, while strictly enforcing type fidelity and type safety. In addition, the managed environment of the runtime eliminates many common software issues. For example, the runtime automatically handles object layout and manages references to objects, releasing them when they are no longer being used. This automatic memory management resolves the two most common application errors, memory leaks and invalid memory references. The runtime also accelerates developer productivity. For example, programmers can write applications in their development language of choice, yet take full advantage of the runtime, the class library, and components written in other languages by other developers. Any compiler vendor who chooses to target the runtime can do so. Language compilers that target the.net Framework make the features of the.net Framework available to existing code written in that language, greatly easing the migration process for existing applications. While the runtime is designed for the software of the future, it also supports software of today and yesterday. Interoperability between managed and unmanaged code enables developers to continue to use necessary COM components and DLLs. The runtime is designed to enhance performance. Although the common language runtime provides many standard runtime services, managed code is never interpreted. A feature called just-in-time (JIT) compiling enables all managed code to run in the native

24 machine language of the system on which it is executing. Meanwhile, the memory manager removes the possibilities of fragmented memory and increases memory localityof-reference to further increase performance. Finally, the runtime can be hosted by high-performance, server-side applications, such as Microsoft SQL Server and Internet Information Services (IIS). This infrastructure enables you to use managed code to write your business logic, while still enjoying the superior performance of the industry's best enterprise servers that support runtime hosting..net Framework Class Library The.NET Framework class library is a collection of reusable types that tightly integrate with the common language runtime. The class library is object oriented, providing types from which your own managed code can derive functionality. This not only makes the.net Framework types easy to use, but also reduces the time associated with learning new features of the.net Framework. In addition, third-party components can integrate seamlessly with classes in the.net Framework. For example, the.net Framework collection classes implement a set of interfaces that you can use to develop your own collection classes. Your collection classes will blend seamlessly with the classes in the.net Framework. As you would expect from an object-oriented class library, the.net Framework types enable you to accomplish a range of common programming tasks, including tasks such as string management, data collection, database connectivity, and file access. In addition to these common tasks, the class library includes types that support a variety of specialized development scenarios. For example, you can use the.net Framework to develop the following types of applications and services: Console applications. Scripted or hosted applications. Windows GUI applications (Windows Forms). ASP.NET applications. XML Web services.

25 Windows services. For example, the Windows Forms classes are a comprehensive set of reusable types that vastly simplify Windows GUI development. If you write an ASP.NET Web Form application, you can use the Web Forms classes. Client Application Development Client applications are the closest to a traditional style of application in Windows-based programming. These are the types of applications that display windows or forms on the desktop, enabling a user to perform a task. Client applications include applications such as word processors and spreadsheets, as well as custom business applications such as data-entry tools, reporting tools, and so on. Client applications usually employ windows, menus, buttons, and other GUI elements, and they likely access local resources such as the file system and peripherals such as printers. Another kind of client application is the traditional ActiveX control (now replaced by the managed Windows Forms control) deployed over the Internet as a Web page. This application is much like other client applications: it is executed natively, has access to local resources, and includes graphical elements. In the past, developers created such applications using C/C++ in conjunction with the Microsoft Foundation Classes (MFC) or with a rapid application development (RAD) environment such as Microsoft Visual Basic. The.NET Framework incorporates aspects of these existing products into a single, consistent development environment that drastically simplifies the development of client applications. The Windows Forms classes contained in the.net Framework are designed to be used for GUI development. You can easily create command windows, buttons, menus, toolbars, and other screen elements with the flexibility necessary to accommodate shifting business needs. For example, the.net Framework provides simple properties to adjust visual attributes associated with forms. In some cases the underlying operating system does not support changing these attributes directly, and in these cases the.net Framework automatically recreates the forms. This is one of many ways in which the.net Framework integrates

26 the developer interface, making coding simpler and more consistent. Unlike ActiveX controls, Windows Forms controls have semi-trusted access to a user's computer. This means that binary or natively executing code can access some of the resources on the user's system (such as GUI elements and limited file access) without being able to access or compromise other resources. Because of code access security, many applications that once needed to be installed on a user's system can now be safely deployed through the Web. Your applications can implement the features of a local application while being deployed like a Web page. Server Application Development Server-side applications in the managed world are implemented through runtime hosts. Unmanaged applications host the common language runtime, which allows your custom managed code to control the behavior of the server. This model provides you with all the features of the common language runtime and class library while gaining the performance and scalability of the host server. The following illustration shows a basic network schema with managed code running in different server environments. Servers such as IIS and SQL Server can perform standard operations while your application logic executes through the managed code. Server-side managed code ASP.NET is the hosting environment that enables developers to use the.net Framework to target Web-based applications. However, ASP.NET is more than just a runtime host; it is a complete architecture for developing Web sites and Internet-distributed objects using

27 managed code. Both Web Forms and XML Web services use IIS and ASP.NET as the publishing mechanism for applications, and both have a collection of supporting classes in the.net Framework. XML Web services, an important evolution in Web-based technology, are distributed, server-side application components similar to common Web sites. However, unlike Webbased applications, XML Web services components have no UI and are not targeted for browsers such as Internet Explorer and Netscape Navigator. Instead, XML Web services consist of reusable software components designed to be consumed by other applications, such as traditional client applications, Web-based applications, or even other XML Web services. As a result, XML Web services technology is rapidly moving application development and deployment into the highly distributed environment of the Internet. If you have used earlier versions of ASP technology, you will immediately notice the improvements that ASP.NET and Web Forms offers. For example, you can develop Web Forms pages in any language that supports the.net Framework. In addition, your code no longer needs to share the same file with your HTTP text (although it can continue to do so if you prefer). Web Forms pages execute in native machine language because, like any other managed application, they take full advantage of the runtime. In contrast, unmanaged ASP pages are always scripted and interpreted. ASP.NET pages are faster, more functional, and easier to develop than unmanaged ASP pages because they interact with the runtime like any managed application. The.NET Framework also provides a collection of classes and tools to aid in development and consumption of XML Web services applications. XML Web services are built on standards such as SOAP (a remote procedure-call protocol), XML (an extensible data format), and WSDL ( the Web Services Description Language). The.NET Framework is built on these standards to promote interoperability with non- Microsoft solutions. For example, the Web Services Description Language tool included with the.net Framework SDK can query an XML Web service published on the Web, parse its WSDL description, and produce C# or Visual Basic source code that your application can use to become a client of the XML Web service. The source code can create classes derived

28 from classes in the class library that handle all the underlying communication using SOAP and XML parsing. Although you can use the class library to consume XML Web services directly, the Web Services Description Language tool and the other tools contained in the SDK facilitate your development efforts with the.net Framework. If you develop and publish your own XML Web service, the.net Framework provides a set of classes that conform to all the underlying communication standards, such as SOAP, WSDL, and XML. Using those classes enables you to focus on the logic of your service, without concerning yourself with the communications infrastructure required by distributed software development. Finally, like Web Forms pages in the managed environment, your XML Web service will run with the speed of native machine language using the scalable communication of IIS. Namespaces Namespaces organize the objects defined in an assembly. Assemblies can contain multiple namespaces, which can in turn contain other namespaces. Namespaces prevent ambiguity and simplify references when using large groups of objects such as class libraries. For example, Visual Studio.NET defines the ListBox class in the System.Windows.Forms namespace. The following code fragment shows how to declare a variable using the fully qualified name for this class: Dim LBox As System.Windows.Forms.ListBox Visual Studio.NET namespaces address a problem sometimes known as namespace pollution, in which the developer of a class library is hampered by the use of similar names in another library. These conflicts with existing components are sometimes called name collisions. For example, if you create a new class named ListBox, you can use it inside your project without qualification. However, if you want to use the Visual Studio.NET ListBox class

29 in the same project, you must use a fully qualified reference to make the reference unique. If the reference is not unique, Visual Basic.NET produces an error stating that the name is ambiguous. The following code snippet demonstrates how to declare these objects: ' Define a new object based on your ListBox class. Dim LBC as New ListBox ' Define a new Windows.Forms ListBox control. Dim MyLB as New System.Windows.Forms.ListBox The following illustration shows two namespace hierarchies, both containing an object named ListBox. By default, every executable file you create with Visual Basic.NET contains a namespace with the same name as your project. For example, if you define an object within a project named ListBoxProject, the executable file, ListBoxProject.exe, contains a namespace called ListBoxProject. Multiple assemblies can use the same namespace. Visual Basic.NET treats them as a single set of names. For example, you can define classes for a namespace called SomeNameSpace in an assembly named Assemb1, and define additional classes for the same namespace from an assembly named Assemb2. Fully Qualified Names Fully qualified names are object references that are prefixed with the name of the namespace where the object is defined. You can use objects defined in other projects if you create a reference to the class (by choosing Add Reference from the Project menu) and then use the fully qualified name for the object in your code. The following code fragment shows how to to use the fully qualified name for an object from another project's namespace:

30 Dim LBC As New ListBoxProject.Form1.ListBox() Fully qualified names prevent naming conflicts because the compiler can always determine which object is being used. However, the names themselves can get long and cumbersome. To get around this, you can use the Imports statement to define an alias an abbreviated name you can use in place of a fully qualified name. For example, the following code snippet creates aliases for two fully qualified names, and uses these aliases to define two objects: Imports LBControl = System.Windows.Forms.ListBox Imports MyListBox = ListBoxProject.Form1.ListBox Dim LBC As LBControl Dim MyLB As MyListBox If you use the Imports statement without an alias, you can use all the names in that namespace without qualification provided they are unique to the project. If your project contains Imports statements for namespaces that contain items with the same name, you must fully qualify that name when you use it. Suppose, for example, your project contained the following two Imports statements: Imports MyProj1 ' This namespace contains a class called Class1. Imports MyProj2 ' This namespace also contains a class called Class1. If you attempt to use Class1 without fully qualifying it, Visual Basic.NET produces an error stating that the name Class1 is ambiguous. Namespace Level Statements Within a namespace, you can define items such as modules, interfaces, classes, delegates, enumerations, structures, and other namespaces. You cannot define items such as properties, procedures, variables and events at the namespace level, these items must be declared within containers such as modules, structures, or classes.

31 Multithreaded Applications With Visual Basic.NET, you can write applications that perform multiple tasks simultaneously. Tasks with the potential of holding up other tasks can execute on separate threads, a process known as multithreading or free threading. Applications that use multithreading are more responsive to user input because the user interface stays active while processor-intensive tasks execute on separate threads. Multithreading is also useful when creating scalable applications, because you can add threads as the workload increases. Creating and Using Threads You create a new thread in Visual Basic.NET by declaring a variable of type System.Threading.Thread and calling the constructor with the AddressOf statement and the name of the procedure or method you want to execute on the new thread. The following code provides an example: Dim MyThread As New System.Threading.Thread(AddressOf MySub) Starting and Stopping Threads To start the execution of a new thread, use the Start method, as in the following code: MyThread.Start() To stop the execution of a thread, use the Abort method, as in the following code: MyThread.Abort() Besides starting and stopping threads, you can also pause threads by calling the Sleep or Suspend methods, resume a suspended thread with the Resume method, and destroy a thread using the Abort method, as in the following code: MyThread.Sleep () MyThread.Suspend ()

32 MyThread.Abort () See Thread States <vaconthreadstates.htm> for more information on thread states and methods. Thread Priorities Every thread has a priority property that determines how large of a time slice it gets to execute. The operating system allocates longer time slices to high-priority threads than it does to low-priority threads. New threads are created with the value of Normal, but you can adjust the Priority property to any of the other values in the System.Threading.ThreadPriority enumeration. See ThreadPriority Enumeration for a detailed description of the various thread priorities. Foreground and Background Threads A foreground thread runs indefinitely, while a background thread terminates once the last foreground thread has stopped. You can use the IsBackground property to determine or change the background status of a thread Changing Thread States Once a thread has started, you can call its methods to change its state. For example, you can cause a thread to pause for a fixed number of milliseconds by calling Thread.Sleep. The Sleep method takes as a parameter a timeout, which is the number of milliseconds that the thread remains blocked. Calling Thread.Sleep(System.Threading.Timeout.Infinite) causes a thread to sleep until it is interrupted by another thread that calls Thread.Interrupt. The Thread.Interrupt method wakes the destination thread out of any wait it may be in and causes an exception to be raised. You can also pause a thread by calling Thread.Suspend. When a thread calls Thread.Suspend on itself, the call blocks until another thread resumes it by calling Thread.Resume. When a thread calls Thread.Suspend on another thread, the call is

33 non-blocking and causes the other thread to pause. Calling Thread.Resume breaks another thread out of its suspended state and causes it to resume execution. Unlike Thread.Sleep, Thread.Suspend does not immediately stop a thread; the suspended thread does not pause until the common language runtime determines that it has reached a safe point. The Thread.Abort method stops a running thread by raising a ThreadAbortException exception that causes the thread to die. See Thread Methods for detailed information about these methods Overview of ADO.NET ADO.NET provides consistent access to data sources such as Microsoft SQL Server, as well as data sources exposed via OLE DB and XML. Data-sharing consumer applications can use ADO.NET to connect to these data sources and retrieve, manipulate, and update data. ADO.NET cleanly factors data access from data manipulation into discrete components that can be used separately or in tandem. ADO.NET includes.net data providers for connecting to a database, executing commands, and retrieving results. Those results are either processed directly, or placed in an ADO.NET DataSet object in order to be exposed to the user in an ad-hoc manner, combined with data from multiple sources, or remoted between tiers. The ADO.NET DataSet object can also be used independently of a.net data provider to manage data local to the application or sourced from XML. The ADO.NET classes are found in System.Data.dll, and are integrated with the XML classes found in System.Xml.dll. When compiling code that uses the System.Data namespace, reference both System.Data.dll and System.Xml.dll. For an example of compiling an ADO.NET application using a command line compiler, see ADO.NET Sample Application <cpconsampleapplication.htm>. ADO.NET provides functionality to developers writing managed code similar to the functionality provided to native COM developers by ADO. For a discussion of the differences between ADO and ADO.NET, see "ADO.NET for the ADO Programmer" at

34 Design Goals for ADO.NET As application development has evolved, new applications have become loosely coupled based on the Web application model. More and more of today's applications use XML to encode data to be passed over network connections. Web applications use HTTP as the fabric for communication between tiers, and therefore must explicitly handle maintaining state between requests. This new model is very different from the connected, tightly coupled style of programming that characterized the client/server era, where a connection was held open for the duration of the program's lifetime and no special handling of state was required. In designing tools and technologies to meet the needs of today's developer, Microsoft recognized that an entirely new programming model for data access was needed, one that is built upon the.net Framework. Building on the.net Framework ensures that the data access technology would be uniform components would share a common type system, design patterns, and naming conventions. ADO.NET was designed to meet the needs of this new programming model: disconnected data architecture, tight integration with XML, common data representation with the ability to combine data from multiple and varied data sources, and optimized facilities for interacting with a database, all native to the.net Framework. In creating ADO.NET, Microsoft embraced the following design goals. Leverage Current ADO Knowledge The design for ADO.NET addresses many of the requirements of today's application development model. At the same time, the programming model stays as similar as possible to ADO, so current ADO developers do not have to start from the beginning in learning a brand new data access technology. ADO.NET is an intrinsic part of the.net Framework without seeming completely foreign to the ADO programmer. ADO.NET coexists with ADO. While most new.net-based applications will be written using ADO.NET, ADO remains available to the.net programmer through.net COM interoperability services. For a discussion of the differences between ADO and ADO.NET, see "ADO.NET for the

35 ADO Programmer" at Support the N-Tier Programming Model ADO.NET provides first-class support for the disconnected, n-tier programming environment for which many new applications are written. The concept of working with a disconnected set of data has become a focal point in the programming model. The ADO.NET solution for n-tier programming is the DataSet. Integrate XML Support XML and data access are intimately tied XML is all about encoding data, and data access is increasingly becoming all about XML. The.NET Framework does not just support Web standards it is built entirely on top of them. XML support is built into ADO.NET at a very fundamental level. The XML classes in the.net Framework and ADO.NET are part of the same architecture they integrate at many different levels. You no longer have to choose between the data access set of services and their XML counterparts; the ability to cross over from one to the other is inherent in the design of both. ADO.NET Architecture Data processing has traditionally relied primarily on a connection-based, two-tier model. As data processing increasingly uses multi-tier architectures, programmers are switching to a disconnected approach to provide better scalability for their applications.

36 XML and ADO.NET ADO.NET leverages the power of XML to provide disconnected access to data. ADO.NET was designed hand-in-hand with the XML classes in the.net Framework both are components of a single architecture. ADO.NET and the XML classes in the.net Framework converge in the DataSet object. The DataSet can be populated with data from an XML source, whether it is a file or an XML stream. The DataSet can be written as World Wide Web Consortium (W3C) compliant XML, including its schema as XML Schema definition language (XSD) schema, regardless of the source of the data in the DataSet. Because the native serialization format of the DataSet is XML, it is an excellent medium for moving data between tiers making the DataSet an optimal choice for remoting data and schema context to and from an XML Web service. The DataSet can also be synchronized with an XmlDataDocument to provide relational and hierarchical access to data in real time. For more information, see Synchronizing a DataSet with an XmlDataDocument <cpconsynchronizingdatasetwithxmldatadocument.htm>. ADO.NET Components The ADO.NET components have been designed to factor data access from data manipulation. There are two central components of ADO.NET that accomplish this: the DataSet, and the.net data provider, which is a set of components including the Connection, Command, DataReader, and DataAdapter objects. The ADO.NET DataSet <cpcontheadonetdataset.htm> is the core component of the disconnected architecture of ADO.NET. The DataSet is explicitly designed for data access independent of any data source. As a result it can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet contains a collection of one or more DataTable objects made up of rows and columns of data, as well as primary key, foreign key, constraint, and relation information about the data in the DataTable objects.

37 The other core element of the ADO.NET architecture is the.net data provider <cpconadonetproviders.htm>, whose components are explicitly designed for data manipulation and fast, forward-only, read-only access to data. The Connection object provides connectivity to a data source. The Command object enables access to database commands to return data, modify data, run stored procedures, and send or retrieve parameter information. The DataReader provides a high-performance stream of data from the data source. Finally, the DataAdapter provides the bridge between the DataSet object and the data source. The DataAdapter uses Command objects to execute SQL commands at the data source to both load the DataSet with data, and reconcile changes made to the data in the DataSet back to the data source. You can write.net data providers for any data source. The.NET Framework ships with two.net data providers the SQL Server.NET Data Provider and the OLE DB.NET Data Provider. The following diagram illustrates the components of ADO.NET architecture the SQL Server.NET Data Provider and the OLE DB.NET Data Provider. The following diagram illustrates the components of ADO.NET architecture ADO.NET architecture

38 Remoting or Marshaling Data between Tiers and Clients The design of the DataSet enables you to easily transport data to clients over the Web using XML Web services, as well as allowing you to marshal data between.net components using.net Remoting services. You can also remote a strongly typed DataSet in this fashion. For an overview of XML Web services, see XML Web Services Overview <cpconwebservicesoverview.htm>. For an example of consuming a DataSet from an XML Web service, see Consuming a DataSet from an XML Web Service <cpconconsumingdatasetfromwebservice.htm>. An overview of remoting services can be found in the.net Remoting Overview <cpconnetremotingoverview.htm>. Note that DataTable objects can also be used with remoting services, but cannot be transported via an XML Web service. ADO.NET Platform Requirements The Microsoft.NET Framework SDK (including ADO.NET) is supported on Microsoft Windows 2000, Microsoft Windows NT 4 with Service Pack 6a, Microsoft Windows Millennium Edition, Microsoft Windows 98, and Microsoft Windows SE. Use of the SQL Server.NET Data Provider or OLE DB.NET Data Provider requires the installation of Microsoft Data Access Components version 2.6 or later.

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